1. Field of the Invention
Embodiments disclosed herein relate generally to antiperspirant compositions. More particularly, embodiments disclosed herein relate to antiperspirant compositions having aluminum or aluminum-zirconium salts with high efficacy.
2. Background Art
Antiperspirant compositions are available in a variety of forms, such as aerosol suspensions; pump sprays; roll-on powders; emulsions or suspensions; and solid gels, waxes or suspensions.
Basic aluminum halides, particularly chlorides such as aluminum chlorohydrates, aluminum sesquichlorohydrate, aluminum dichlorohydrate, and the like, as well as aluminum nitrates, have been known and used for years as antiperspirant agents. In general, the aluminum compounds are complex structures comprised of mixtures of polymeric and monomeric compounds having various sizes and molecular structures, together with varying amounts of bound or coordinated water. The compounds can generally be represented by the simplified empirical formula, Alx(OH)yY(3x-y), where 0<y≦3x, x≧1, and Y is one or more of chloride, bromide, iodide, or nitrate ions. However, this empirical formula is simplified and is intended to include basic aluminum chlorides containing coordinated or bound molecules of water, as well as basic aluminum chloride polymers, complexes, and mixtures thereof. Aluminum chlorides where x is 2 and y is 1, i.e., Al2(OH)5Cl, is generally referred to as 5/6 basic aluminum chloride, and has been recognized as the standard active ingredient for antiperspirants for many years.
Aluminum chlorohydrates, as well as other aluminum salts, such as aluminum chlorohydrex (complexes of aluminum chlorohydrate with propylene glycol or polyethylene glycol) and aluminum zirconium glycine salts, are known to contain a variety of polymeric and oligomeric species with molecular weights ranging from 100 to 500,000.
The aluminum and/or zirconium salts are formed by partial neutralization of acidic aluminum (Al3+) and/or zirconium (Zr4+) metal ions. The partial neutralization of these ions results in the formation of aluminum and zirconium hydrolysis products of complex structure. The performance (i.e., efficacy) of aluminum and aluminum-zirconium salt compositions is dependent on the molecular distribution of these hydrolysis products. In general, low molecular weight hydrolysis products favor better performance by providing increased sweat inhibition, i.e., increased efficacy. Specifically, it has been clinically shown that the smaller the species, the higher the efficiency on sweat reduction.
Aluminum and aluminum-zirconium antiperspirant salts function by forming insoluble metal hydroxides in the ducts of sweat glands. This blockage prevents perspiration. Low molecular weight salts penetrate more deeply into these ducts than their high molecular weight counterparts. Thus, deeper penetration provides more effective blockage.
Accordingly, there exists a continuing need for developments in antiperspirant compositions having increased efficacy.